The present invention relates to a method for rapid and accurate qualitative and quantitative analysis of a finishing agent applied to the surface of a glass fiber substrate.
Hitherto, as a method for qualitative and quantitative analysis of finishing agent on glass fiber substrate for printed wiring boards, there has been known "New Qualitative and Quantitative Analytical Method for Coupling Agent on Glass Cloth" Preprint Section 18-A (1961) of The Society of the Plastics Industry, Inc. This method utilizes color reaction of indicators (Methylene Blue method, Bromocresol Green method, etc.). In Japan, ignition of loss method according to JIS-R-3420 has been widely employed for quantitative analysis.
Printed wiring board are necessarily dipped in a molten solder bath during production of the printed wiring board and a significant problem is separation of glass cloth and epoxy resin at their interface due to thermal shock at the dipping.
This interfacial separation is greatly affected by properties of the finishing agent for glass fiber substrate. Therefore specifying the kind of the finishing agent and weighing thereof must be carried out accurately and rapidly.
Analysis of a the finishing agent applied to the surface of glass fiber substrate which greatly affects the performances of printed wiring board has been conducted by ignition of loss method which comprises heating a sample to 625.degree. C. to burn the finishing agent which is an organic material.
However, this ignition of loss method has the following defects: (1) Qualitative analysis of finishing agent is impossible; (2) Measurement requires very long time; (3) Accuracy of quantitative analysis is not high.
Quality assurance of printed wiring board by the ignition of loss method cannot sufficiently express the state of finishing agent and besides rapid measure is impossible because of long time required for measurement.
Analysis of a finishing agent applied onto the surface of a glass fiber substrate by infrared absorption method is also attempted. (See, for example, "Sen-i Gakkaishi" vol. 43 (1987) page 313 and "Applied Spectroscopy", vol. 38 (1984), page 1). However, according to such a method, when the amount of finishing agent contained in the sample is small and especially when the deposition amount of finishing agent is small because the surface area is small as in industrial products which are relatively large in fiber diameter the, spectrum is indefinite and the analysis is difficult.